Originally posted by vonBaloney Could just be that someone took it apart and cleaned the elements, and left a little swirl. When you sell it, just say that it is there and has no effect on IQ...
I don't think it was opened. The original seller said he didn't, and despite him missing the eroded coatings in the first place, I'm going to believe him. I certainly didn't, as I've opened up an F series AF lens before and totally junked it in the process.
It's fine though, it's really not that bad. Even two of the guys at my camera store had a hard time spotting it. If I hadn't been so paranoid about checking my lenses, I probably would have missed it too.